Talk about a slippery slope. Preventing people from intentionally lowering their rank; okay, I can accept that. But limiting them to one account per copy? This has some serious side effects, which they may have intended.
What happens when I get bored with SC2 and want to sell it or give it away? The new owner can't create his own account, so I have to give him mine. But that account has my name, password, and email address associated with it, none of which I want to give up to him, and he likely doesn't want to be stuck with those either. Many new games have this same problem and they do it intentionally to squash the second-hand market.
As a consumer, I expect to be able to get value out of what I buy. That means playing it, enjoying it, and when I'm done with it, reselling it. This is especially important if I don't enjoy it, because I can't return it, so I had better be able to resell it for basically the same price I bought it for. I could do this if a used copy were just as good as a new copy, but companies are building in all sorts of pitfalls to ensure this isn't the case, devaluing used copies (which is my copy the second I buy it) and encouraging new purchases.
They say it is there to prevent gaming the matchmaking system, but it also kills the second-hand market, which is something they also want, and which gamers should be angry about. Killing the used market is just as bad as DRM -- it punishes those who legitimately purchase games.
